Okay, opinions please...

I have a Comfrey plant that someone gave me in June. It was a feeble
little thing when I got it but now it is like a show plant -- absolutely
huge, lush and vivid dark green. The root ball would probably fill a
bushel basket. I know if I leave it here, it will probably be mowed down
and destroyed and I'm wondering if it is worth it to move it? And if I try
to move it, how much can I cut it back (tops and/or roots) before I damage
it fatally? I'm taking a lot of my favorite smaller herbs with me because
I can't stand the thought of them being slaughtered but this is by far the
biggest outside plant I'm thinking of moving. My thirty-five year old Xmas
Cactus is the biggest indoor plant I'm moving.